Baking soda in a pinch

[golfsuper]

Just a quick question,

I am still struggling with low alkalinity in my four month old reef tank. Seems to hover between 1.7 and 2.2 meq/l. The tank is a 75g with 90 lbs of fiji transshipped live rock, and 4+ inches of aragonite(s). I am currently dosing with Seachem's Reef Builder during the day and following up with Kalkwasser at night (calcium seems a tad low at about 325 ppm). I was told by a lfs that Seachem has had a small problem with a batch of their Reef Builder keeping alk above 2.2, and I understand this may also be related to "new tank syndrome", but is baking soda a viable alternative? I have done weekly 15 gal. water changes to cover that end, but I seem to be in a holding pattern. What do you all think? Any suggestions would be appreciated. Thanks

golfsuper

[susie]

Someone will correct me if I'm wrong but I believe baking soda will only raise the pH and not the alk.

[PowrPlay]

What animals do you have in the tank?

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Improve your Digital Photos (http://www.jps.net/powrplay/DCpix.html) :)
"Ok, ok, this is all I'm getting!"

[Carlos]

Well, your LFS is right (for once :D). Seachem products do tend to bring your alkalinity down but that is something that can be corrected. I dose Reef Advantage to my tank once a week and what I do is I buffer all the makeup water. This way, buffered water is slowly introduced to the tank keeping the alkalinity at a normal level. Also, by introducing it slowly, chances of having calcium precipitation are minimized unless you alkalinity goes way high.
I use Kent Marine Super Buffer for the make up water and have not had any problems at all.

HTH,

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Carlos
Carlos' Great Barrier (http://www.ntsource.com/~cchaco2)
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Please, take care of the ocean and its inhabitants. They're all we've got!

[cory]

Susies right.

[Kenzy]

Unless my test kits and pinpoint PH monitor that was just calibrated are way off I beg to differ with Cory and Susie. I use good ole Arm & Hammer baking soda if I forget to pick up some buffer (usually Kent).

I don't think I would recommend using it all the time, but from what I've seen and tested it will raise alk quite well with little effect on PH. Now I'm not a chemist and this is only what I've seen in my own tanks. Take it for what you will. :)

[OrionN]

Kenzy is right. Baking soda is NaHCO3. It raise Carbonate and Bicarbonate in our tank.

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Minh Nguyen
Visit my reef at:
http://sites.netscape.net/austinnguyen/homepage

[golfsuper]

Thanks for the responses everybody. Seems as though we have a difference of opinion here. My bioload is relatively light at this time with only a pair of false percs. and some small frags of sps and softies. The rock cycled very quickly, but half of the 90 lbs was a fiji "plant" rock that had lots of brown-leafed macro algae on it (if it is macro algae at all). I'm wondering if that may be holding down the alk somehow. There is no decay to speak of, but it has tinted the water slightly. Any thoughts?

golfsuper

[Michelle]

But what will raise pH? I know that once it's up there, the alk will help maintain it, but how to get it up there in the first place? The pH in my tank is a rather low but steady 7.8. Everything in the tank seems fine with it, but would probably like it better if it was up so 8.3-4 or so.

Thanks,
-Michelle

[jimhobbs]

Muhuuuum, seems like I remember Frank Grecco discussing the missing components of baking soda; and the fact that it wasn't "complete" in all the necessary ions for buffering...I can't seem to recall what the outcome would be if used on any type of continuous basis...

Hey SteveR,
Do you remember anything about that?...I seem to recall you discussiong something of this nature with him... :)

Sorry I couldn't be of more help; but I personally wouldn't use it...Best regards...jim :)

[This message has been edited by jimhobbs (edited 06-11-2000).]

[Steve Richardson]

golfsuper -

I suppose I'll throw my 2 cents in here.. :)

It sounds like you are adding reefbuilder every day, which you should not have to do. You are using kalkwasser too, which should actually keep your consumption of buffer additive down.

How much kalk are you adding? If you add too much, it can actually errode your buffer since it can spike your pH. A guideline I give to people who are starting to use kalk is 1% of tank water volume in an 8 hour period. So... if you have a sump, and perhaps have 60 gallons of water total in your system... you might want to start with about 1/2-3/4 gallon of kalk at night, and see how it goes.

Thats another question - whats your pH averaging, and are you watching it closely? How long have you been adding kalk?

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regarding the baking soda issue... The buffers that we buy are mixtures of several ingredients... bicarbonate mostly, but also carbonate, and borate... probably some other things I dont even know about ( ;) ), but the point is, is that each ingredient has a different pH... and it all "Adds up" to a pH of about 8.3.

Using baking soda only will indeed increase your alkalinity... but over time, you might see your pH drift towards 7.8-ish since that (I think) is the pH of bicarbonate. Its much more complicated than that... and your system will manufacture its own carbonates etc.... and you may also be doing water changes which will also help to keep things normal.

In a pinch, I suppose bicarbonate is O.K... but I would stick with a balanced buffering additive. I happen to use reefbuilder occasionally, and think its a good product. I would dissagree that it "tends to bring your alkalinity down. My alk has always been around 10 dKH / 3.5 meq -ish. ;)

If they had a bad lot, thats another issue.

You will find 2 types of buffers out there... ones that will effect pH and ones that will not so much. eg - ReefBuilder primarily acts on alkalinity, and the other product they carry MarineBuffer will have a more dramatic effect on raising pH too. Just read the labels... they should describe the effect on thr pH. I'm sure you will get many suggestions on which ones people like.

hth a little...

-Steve

[OrionN]

golfsuper,
Read and understand pH and Alkalinity chemistry in our aquarium. It will not be a waste of time. The bare-bone basic is that CO2, HCO3-, CO3-- all exist in equilibrium in our tank according to this equation:
2(H+)+ CO3-- <->H+ + HCO3- <-> H2O + CO2
These chemicals change state million of time per second. Not only they are in equilibrium with each other, they are also in equilibrium with other - and + ions in the water. These ions are the main ones that account for the pH of the water. pH is essentially the inverse log of the concentration of H+.
I cannot go to everything in detail here but if you check into some of Craig Bingman writing online he does a much better in explaining the detail.


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Minh Nguyen
Visit my reef at: http://sites.netscape.net/austinnguyen/homepage

[This message has been edited by Minh Nguyen (edited 06-11-2000).]

[Steve Richardson]

Minh - Yup. Its always good to try and soak up the basics... I figure with all the Chemistry, Biology, Ecology, Zoology, Morphology, Anatomy, ... heck, Plumbing ( ;) ), that in about 20 more years... I still wont know what I'm doing. :D

Fun to keep trying though. :)

Some of Bingmans stuff can be read in the RC Library here:
http://www.reefcentral.com/library/CraigBingman.htm

-S

[golfsuper]

Steve and Minh,

Thanks again for your replies. Steve, to answer your questions, I am adding kalk at 1 gal./day (1/2 tsp per gal.) dripped in during the night. The ReefBuilder is dripped during the day, which together constitutes the bulk of my make-up water in a 24hr period. Interestingly, my pH has remained fairly high, averaging 8.4 to as high as 8.6 for brief periods (during kalk dosing in particular).

To Minh and Steve (and others), I have a crude understanding of the pH and alk process through my agronomic background, but what puzzles me is what is holding these two (or possibly 3) parameters back? I feel as though I should be approaching this from an analytical standpoint, much like finding the source of Phosphates when trying to solve a hair algae problem. So what "culprit" might I be looking for? Is it simply part of the cycling process, only months from the initial cycle? Do I run the risk of throwing things way off kilter by chasing these two issues at the same time or am I making a mountain out of a mole hill? Someone tell me to shut up now. Sorry.

golfsuper

[tdwyatt]

Hey folks, I will post this (an old THREAD on AOL) that you can use to get a general ideas of how the carbonate/bicarbonate chemistry works in the tanks. I believe it is archived somewhere, but not sure. It contains the chemistry and the physics, as well as the how and why (sometimes oversimplified) of the alkalinity/buffering of seawater. Just my two cents, if you need references, I will be glad to supply a bibliography for this.

Later, Tom <"{{{{>(
OK, class is in session! Here's a primer on pH, Carbonate hardness (as opposed to alkalinity and hardness), and calcium ion concentrations in relation to these variables, and the role of dissolved atomopheric gasses (in particular, CO2) in the acid base equilibrium game.

Seawater is made up of seven primary salts called the conservative elements. These are always in the same proportion to each other regardless of the salinity, temperature or pH of seawater.They make up about 99% of the dissolved inorganic solids in seawater. They are sodium chloride (NaCl), magnesium chloride (MgCl2), magnesium sulfate (MgSO4 and it's many hydrates), calcium sulfate(CaSO4), potassum sulfate (K2SO4), calcium carbonate (CaCO3), and potassium or sodium borate. These are always in the same proportion in seawater to each other, regardless of the salinity of that seawater. What WE are primarily interested in in this discussion is calcium, carbonate, bicarbonate, and to some extent, borate. These compounds make up the bulk of the BUFFERING capacity of seawater.

The buffering capacity of seawater is it's ability to resist changes in the concentration of Hydrogen ions (change in pH). Hydrogens ions are the ions responsible for INCREASES in ACIDITY, which translates to DROPS in pH. Acids are substances that when in aqueous media like seawater, dissociate to form a cation of hydrogen and an anion that may or may not contribute to the buffering capacity of seawater. Once we introduce life into seawater, we begin to accumulate waste products that are most often acidic; that is, they dissociate in water to provide hydrogen ions. The buffering capacity of an aqueous system is its ability to neutralize these hydrogen ions so that there is NOT an increase in the total hydrogen ion concentration (which would be an increase in acidity, or a decrease in pH, both of these terms are synonymus)

Alkalinity, carbonate hardness, the carbonate-bicarbonate system, total hardness, and pH are all terms that are used to help describe the buffering system of seawater. It is a dynamic system of equilibria that exists to prevent drastic changes on the reef in terms of hydrogen ion concentration (pH). The buffering system works like this. All ions that are in seawater have the ability to interact and form compounds with other oppositely charged ions. As an example, the sodium from sodium chloride can interact with the borate from potassium borate and temporarily form sodium borate. Due to their high solubility in water and high reactivity, these compounds form and dissociate (unform) rapidly in seawater. This association/dissociation occurs with all inorganic and many organic compounds that ionize in seawater. The rate at which some compounds are formed may be faster or slower for each compound formed,
and is based on the "attractiveness" of each cation and anion. However, ultimately the rate of association/disassociation balences out, and the rate at which this occurs is called EQUILIBRIUM. This can be affected by concentration of the disassociated ions, the concentration of the product(s) of the combination of these ions, the water's temperature, and pressure (either atmospheric or due to depth). Usually a higher concentration on either side of an equation will drive the reaction in the opposite direction (ie, more ions yields more product, until a new equilibrium point is established). For our purposes, temperature USUALLY drives the reaction toward dissassociation, as does pressure. This is why many solutions precipitate as the temperature drops, and we see precipitation of inorganic "nodules" in deep abyssal basins. (too long, I know, but it is in depth, part 2 follows)

Part 2:

Just as the major driving force in downward pH shifts in the aquarium and natural seawater is the production of animal and bacteriological wastes and respirations (CO2), the upward driving force for pH is either the removal of these wastes (ie current or Photosynthesis) or the neutralization of these wastes by the anions that are capable or receiving a cation. The effect of carbon dioxide (CO2) that we are interested in is it's effect on the buffering system. As CO2 is dissolved in seawater, it reacts with with the hydrogen of water to form carbonic acid (H2CO3), a weak acid at best, but a compound that very rapidly dissociates to release it's hydrogen ion (and drive DOWN pH). If CO2 is added to solution too rapidly, equilibrium shifts from the free reactants (CO2 and H2O) to the carbonic acid product rapidly (H2CO3), then dissociates into it's new products, the Hydrogen ion and Bicarbonate (H+ + HCO3-); This also occurs very rapidly, and although it produces bicarbonate as a by-poroduct, the next dissociation occurs much more slowly. Remember that all ions are free to interact with other oppositely charged ions ... and that dissociations occur based on the affinity, or lack thereof, of the anions and cations and the relative concentration of products verses reactants. Carbonic acid rapidly can dissociate (rapidly) into
HCO3- (bicarbonate) then to CO3--(carbonate) (slowly) which in the presence of Calcium cations forms CaCO3 (Moderately), which has a very low solubility in seawater. Generally the equilibrium works like this:

CO2 + (H+) +(OH-) (water) <--> H2CO3 <--> HCO3- & CO3-- (plus dissolved Ca++ from seawater) <-> CaCO3

Note that the arrows point both directions, the reactions go both ways based on the concentration of H+ in the water. If the concentration is driven to the right, either by high concentrations of Calcium ions, or by HIGH concentrations of hydrogen ions, this will increase the concentration of Ca CO3 to the point where it excees it's solubility in water, and it will precipitate out of solution. In a closed system such as our aquaria, the concentration of calcium in seawater is controlled by this dynamic equilibria and the solution will be "saturated" as long as there is CaCO3 in the aquarium. This is why it is so important to increase the buffer capacity of the aquarium in order to maximize the Ca concentration for our corals. Addition or deletion of CO2 above or below atmospheric equilibrium can temporarily change the pH of the solution, but it will not change the carbonate composition of the water (know why?, the hint is : atmospheric EQUILIBRIUM, email me if you can't figure it out ;-) Calcium carbonate that has precipitated out of solution can redissolve and play a role in the equation once the concentration of Ca++ for that pH (hydrogen ion concentration) goes below saturation, however, in reef tanks, corals, mollusks, fish and crustaceans all remove Ca++ from solution as part of their normal metabolism. Therefore, unless we replace Calcium (aragonite sand, Ca reactors, additives/Kalkwasser) as the conc of Ca++ drops, the buffer capacity of the solution will drop in terms of the dissociation of CaCO3 back into the Carbonate/Bicarbonate equilibrium, possibly to the extent that an excess of these reactants, (view these now as products of the CO2/H2O rxn) can drive the reaction to the left, and CO2 will exceed it's saturation in seawater and dissipate into the atmosphere, thus reducing the buffer capacity of the solution. Furthermore, Photosynthesis of plants can reduce (temporarily) the conc of CO2 in the tank while the lights are on via their anabolic processes (plants use CO2 to make carbohydrates and related carbon compounds by stripping off O2 via chlorophyll and utilizing the carbon) This is why we see a pH shift upward during the "on" part of our photoperiods. Rapid increase

[reg]

[Gus Paz]

ahhhh, ya , what he said... :eek:

[golfsuper]

Tom,

Can you repeat that? Just kidding...whew, that was more than I expected but thanks a ton everyone! I'm well into day two of digesting that dissertation, and if my pea-brain can comprehend the information you indulged me with I should crack this nut. Now if I can just figure out how to keep the glass clean...

golfsuper